Here a recapitulation of usesful C and some quick notes on C++ peculiarities – sorry – features: (That might be a good place to start.)

Initialisation
int a = 1; // standard c way
int b(1); // same

Defined constants
#define PI 3.1415927 // faster than var

Declared constants
const int c = 100 // immutable

Assignment
= can also be used as rvalue
a = 1 + (b = 2);

same as:
b = 2;
a = 1 + b;

Comma operator
a = (b=3, b+2); // a = 5

When the set of expressions has to be evaluated for a value, only the rightmost expression is considered

Type casting
int i, j;
float f = 1.234;
i = (int) f;
j = int (f);

sizeof()
One parameter, either a type or a variable and returns the size in bytes.

a = sizeof (char);

Will become important with arrays.